When——（问题出现）,they tried hard to find the solution 为什么用“the problem came up”

When——（问题出现）,they tried hard to find the solution 为什么用“the problem came up” 一个线性代数问题：证明AB-BA不等于E设A、B为两个n阶矩阵,证明：AB-BA≠E.但是你的证明不正确，因为Tr（AB）=Tr（A）*Tr（B）不成立，例如，取B=E，则Tr（AB）=Tr（AE）=Tr(A),而Tr（A）*Tr（B）=Tr（ TR they always have fun_(talk)to each other2._（unfortunate）i don't have enough money to travel abroa3.—of us went to see the basketball game because we had an art classA.one B.none C.some D.no one4.lucy and lili enjoyed themselves on the school tr They often talk about their business when they are haveing lunch.同义句They often— — theirbusiness__ __ ------.They often___ their business ____ ____ _____. Many of the students are _shy_ when then they speak English?(对划线部分进行提问）—— ——many of the students when they speak English. the audience applause with ————（excite）when they saw their favorite moive stars. Did the couple start any hobbies when they retired?改写句子,保持句意不变,Did the couple —— —— any hobbies when they retired, —Could you tell us_______?---For more than ten years.A.when have they got married B.how long they have been married?C.when they had been married?D.how long they had got married?选择的原因也说下吧. ——the farms have been to the US.___really?when there?a.did they go b.have they gone ——they were young ,they showed some signs of being experienced A Until B when c becauseD Though 选词填空 1、when 2、what 3、who 4、where ——are they?They are Mingming’ s grandparnts tr（）ed 中间填什么 英语主动与台改为被动语态1 we should speak to the old men politely 2 Did your mather buy a present buy you a present birthday?3 when do they clean the desks and chairs every week?4 they have not watered the flowers 5they will plant more tr —When did they finish________these pictures?__Yesterday afternoon.A.to drawB.drawingC.drawD.drew AP经济学两个小问题机会成本的公式 两种商品产量的比值为什么会有单位比如 op cost of wheat=2 wine/1 wheat= 2（wine）还有一个 书上说TR=P*Q Q和P分别上升 下降20% TR不变但是我觉得 0.8P*1.2Q=0.96TR 应 When they were When are they